We propose to identify neuronal reactions in spinal cord injury, correlate these reactions with pathological changes, and determine the contribution of neurophysiological events to injury processes in the spinal cord. The experiments will emphasize measurement of extracellular potassium and calcium ions in impacted spinal cords and how they affect blood flow. Specific pharmacological and surgical intervention will be used to manipulate blood flow and ascertain the role of blood flow changes in spinal cord injury. The overall goal of the research is to determine pathophysiological mechanisms in spinal injury and to provide a rational basis for developing effective therapy aimed at the acute phase of spinal injury. In the past year, our research has provided key evidence for the role of ischemia in spinal cord injury, yielded information concerning the interaction of extracellular potassium levels with spinal blood flow, and implicated the peripheral sympathetic system and localized release of endogenous opiates as important factors in spinal injury. In addition, we have established certain electrophysiological criteria for assessing prognosis within the first three hours of spinal injury, developed a method of creating localized lesions of the spinal cord with ultrasonic vibrations, and standardized a technique of measuring blood flow in the spinal cord with small electrodes.